Mechanical power amplifiers



' Oct. 20', 1959 D. N. macmmm 2,909,069

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ATTORNEYS Oct. 20, 1959 D. N. M DONALD 2,909,069 uECHAnIcAL'PowERAMPLIFIERS Filed Dec. 20, 1954 2 Sheets-She et 2 me. a

- CLOSED LOOP - ssm/o 63 55 srsrsu INVENTOR. DUNCAN M MACDONALD BY mid;711-14.

1 A TTORNEVS United States Patent 2,909,069 I MECHANICAL POWERAMPLIFIERS Duncan N. MacDonald, Arcadia, Califl, assignor, by mesneassignments, to Consolidated Electrodynamics Corporation, Pasadena,Calif., a corporation of California Application December 20, 1954,Serial No. 476,422 3 Claims. (Cl. 74-25) This invention relates tomechanical power amplifiers and more particularly to apparatus forconverting a relatively small amount of electrical energy into a strongmechanical force capable of moving heavy loads in a very short time.

In various types of installations, for example, computer systems inwhich magnetic tape must be accelerated and decelerated at high rates,and hydraulic servo-systems in which high speed sliding valves must beoperated, relatively large mechanical loads must be moved in very shorttimes. Quite often the movement of the heavy loads must be in responseto electrical signals. Thus, there is presented the problem of movingheavy loads in a very short time in response to an electrical signal. Asolenoid is a well known device which converts electrical energy intomechanical movement. However, in order for a solenoid to move a heavyload directly, the solenoid requires actuating coils with many turns ofwire and heavy moving parts. These requirements are detrimental to quickoperation due to the electrical and mechanical inertia of the system.

This invention solves the problem of moving heavy loadselectromagnetically in a very short time by using a high speedconventional clapper-type solenoid in conjunction with a motor drivencapstan or power drum around which is disposed an actuating band adaptedto be connected to a relatively heavy load. The solenoid has a lightweight plunger or clapper which reacts almost instantaneously inresponse to an electrical signal to exert a slight force on theactuating band and drive the band into driven relationship with therotating power drum. Since the power drum is rotated at a relativelyhigh speed, practically no inertia delay is present and the large amountof power available in the power drum is applied almost instantaneouslyto the actuating band.

In a presently preferred embodiment of the invention,

the actuating band is wrapped loosely around the rotatable power drum.One end of the band is arranged to be connected to the load and theother end of the band is connected to move in response to the movementof the plunger of the solenoid. Thus, when the solenoid is actuated, thelight-weight plunger moves swiftly to take the slack out of theactuating band and cause it to be drawn tightly around the rotatingpower drum. In this manner a large force is applied almostinstantaneously to the actuating band and the load in response to theslight move ment of the light-weight plunger in the solenoid. With thisarrangement of the length of the power stroke is approximately equal tothe distance through which the plunger moves. As used in this invention,the term actuated as applied to a solenoid includes either energizing orde-energizing the solenoid.

In another form of the invention where relatively long power strokes maybe obtained, the plunger of the solenoid is arranged to move a rollerpositioned adjacent the power drum so that the actuating band is forcedagainst the power drum. Thus, the length of the power stroke isindependent of the length of travel of the plunger.

e 2,909,069 Patented Oct 20, 1959 In another arrangement for obtainingrelatively long strokes, the actuating band is disposed aroundarotatable power drum and an idling drum. The plunger of the solenoid isarranged to force the band into driven relationship with the power drumby either removing the slack from the band or pressing the bandagainstthe power drum. j

For obtaining movement of the load in either one of two directions, tworotatable power drums are arranged to drive a common band in oppositedirections, and a separate solenoid is used with the band to be moved ineither one of two directions in response to an electrical signal. Thisprovides a fast action servo-drive which may be connected in a closedservo-loop system for driving recorders, plotters, computer systems andthe like.

These and other aspects of the invention will be more completelyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which: a

Fig. 1 is a schematic front elevation of the presently preferredembodiment of the invention;

Fig. 2 is a side elevation taken on line 22 of Fig. 1;

Fig. 3 is a schematic front elevation of an alternate embodiment of theinvention; g

Fig. 4 is a side elevation taken on line 44 of Fig. 3;

Fig. 5 is a schematic elevation of yet another embodiment of theinvention; and i Fig. 6 is a schematic illustration of how the inventionmay be employed to drive an actuating band connected to a closed loopservo-system.

For purposes of illustration, the embodiment of the invention of Figs. 1and 2 is shown arranged to actuate a tape driving mechanism 10 as forexample in an electronic computer (not shown). One end of an actuatingband 11, which may be a flexible steel band, is connected to a first arm13 rigidly attached to a pivot 15. An idling roller 17 is carried at theouter end of a second arm 18 rigidly attached to the pivot 15 and isdisposed adjacent the periphery of a tape driving wheel 19. A strip ofmagnetic tape 21, which is to be intermittently fed through thecomputer, passes between the periphery of the driving wheel and theidling roller so that when the arm 13 is rotated about pivot 15 in aclock-wise direction as viewed in Fig. l, the tape is forced into drivenrelationship 'with the driving wheel.

The arm'13 is biased in a counter-clockwise direction (as viewed inFig. 1) by means of a tension spring 23 attached to the first arm.Several turns of the actuating band are loosely wrapped around arotatable power drum 25 adapted to be driven at a high rate of speedaround a shaft 26 by any suitable driving means (not shown). The end ofthe actuating band remote from arm 13 is connected to a clapper 27provided on a conventional clapper-type solenoid 28. A circuit 30 forapplying an electrical signal to the solenoid is-shown schematically asa battery 31 and an off-on switch 32. However, the solenoid may bearranged to receive a signal from any-kind of electrical circuit such asthat employed to control the movement of magnetic tape in a computersystem. 7 .1

The operation of the apparatus of Figs. 1 through 2 is as follows: Withthe solenoid not energized as shown in Figs. 1 and 2, the actuating bandis loosearound the power drum and arm 13 is in the position illustrated,so that the magnetic tape is not'forced against the driving wheel. Inorder to cause magnetic tape to be delivered to a computer, the switchis closed (i.e., a signal calling for magnetic'tape is applied to thesolenoid) and the clapper is pulled in a downward position. The clapperpulled snugly around the power drum. The friction between the power eachpower drum to cause drum and the actuating band is sufiicient to apply astrong downward force on the first arm 13 for the shaft 15 to cause theidling roller to move the tape into driven contact with the drivingwheel. When the energizing signal is removed from the solenoid, theclapper returns to-its original position so that the band is no longerin driven relationship with the drum, and the spring 23 returns thepivot 15 to the position shown in Fig. 1 so that the magnetic tape isnot longer driven.

Using the arrangement shown in Figs. 1 and 2., an 8 pound load was moved.005 inch in an operate time of 3 milliseconds and the same load wasreleased in 1.7 milliseconds. This performance is more than ample foruse in conventional computer systems employing magnetic tape.

The arrangement shown in Figs. 3 and 4 may be used where relatively longpower strokes are required. In this embodiment an actuating band 35 isloosely wound around a rotatable power drum 37 adapted to be driven by apower shaft 39 turned by any suitable means (not shown). One end of theactuating band is connected to a load shown schematically as a tensionspring 40, the other end of the band is fastened to a light-weighttake-up spring.

An idling roller 41 is disposed adjacent the power drum periphery and isconnected to the outer end of an arm 42 carried by a clapper 43 of aconventional clapper-type solenoid 44. A circuit 45 shown schematicallyas a battery 46 and an off-on switch 47 is connected to energize thesolenoid intermittently.

In the position shown in Fig. 3, the solenoid is in a deenergizedcondition and the idling roller is not pressing the actuating bandagainst the power drum. When the solenoid is energized, the clapperforces the roller against the actuating band which in turn is forcedinto driven relationship with the power drum. Thus, the load may bemoved through a relatively large distance almost instantaneously andindependently of the length of travel of the clapper.

Fig. illustrates another arrangement in which a load can be moved almostinstantaneously through a relatively longdistance independent of thelength of travel of the clapper. An actuating band 48 in the form of anendless belt is loosely disposed around a rotatable power drum 49 and anidling drum 50. The power drum is constantly rotated in a clock-wisedirection as viewed in Fig. 5 by any suitable driving means (not shown).A projection 51 on the band located between the two drums is connectedto a load illustrated schematically as a tension spring 52. An idlingroller 53 is connected by an arm 54 to a clapper 55 of a conventionalclapper-type solenoid 56 disposed adjacent the actuating band andarranged to be intermittently energized by a circuit 57 shownschematically as a battery 58 and an off-on switch 59.

When the solenoid is energized, the idling roller is forced against theactuating band to remove the slack from the band so that the band isforced into driven relationship with the power drum.

The embodiment of Fig. 5 may also be arranged with the solenoid adjacentthe power drum periphery so that when the solenoid is energized, theidling roller forces the actuating band against the power drum.

Fig. 6 shows another embodiment of the invention for moving a load ineither one of two directions. A first power drum 61 is arranged torotate in a counter-clockwise direction, as viewed in Fig. 6, and asecond power drum 62, spaced from the first, is arranged to rotate in aclockwise direction. An actuating band 63 in the form. of an'endlessbelt is loosely wound around each of the drums with several turns. Oneend of a mechanical link 65 is rigidly attached to this band and theother end of the link is connected to feed mechanical movement to a.load or movable mass 66 in a closed loop servesystem 67 shownschematically in block form. The closed loop servo-system may be arecorder using the self-balancing potentiometer principle, a plotter, acomputer system, or the like.

A first conventional clapper-type solenoid 68 is disposed adjacent theband between the mechanical link and the first power drum. A firstidling roller 69 carried by an arm 70 connected to a clapper 71 of thefirst solenoid is arranged to take the slack out of the band between theload and the first power drum when the first solenoid is actuated andthus cause the band to move upwardly. A second conventional clapper-typesolenoid 73 is disposed adjacent the actuating band between the link andthe second power drum. A second idling roller 75 is carried by an arm 76connected to a clapper 77 of the second solenoid and arranged to takethe slack from the band between the link and the second power drum whenthe second solenoid is actuated. Each solenoid is electrically connectedto receive appropriate signals from the closed loop servo-system. Thus,when the closed loop servo-system calls for the link to be moved up, thefirst solenoid is actuated and the link moves up until the servo-systemis balanced and the first solenoid is deenergized. If the closed loopservo-system calls for the load to be moved downwardly, the secondsolenoid is energized and the link is moved down until the system isonce again balanced and the second solenoid is deenergized.

In all of the above arrangements the tape is shown being forced intodriven relationship when the solenoid is energized, i.e., suppliedelectrical power. However in any of the above arrangements, the clapperof the solenoid may be spring loaded so that the tape is held in drivenrelationship until the solenoid is energized and the clapper overcomesthe action of the spring to release the band from driven relationship.With either arrangement the invention provides means for converting arelatively small electrical signal and a correspondingly smallmechanical movement of a light-weight element into a relatively largeamount of mechanical power almost instantaneously with the generation ofthe electrical signal.

I claim:

1. A mechanical power amplifier for applying power to a load in eitherone of two directions comprising a first power drum, means for rotatingthe first power drum continuously in one direction, a second power drum,means for rotating the second power drum continuously in the oppositedirection from the first drum, an actuating band disposed around-thedrums, and adapted to be connected to the load, a first solenoid havinga plunger arranged to move the band into driven relationship with thefirst drum when the first solenoid is actuated, and a second solenoidhaving a plunger arranged to move the band into driven relationship withthe second drum when the second solenoid is actuated.

2. A mechanical power amplifier for applying power to a load in eitherone of two directions comprising a first power drum, means for rotatingthe first power drum continuously in one direction, a second power drum,means for rotating the second power drum continuously in the oppositedirection from the first drtun, an actuating band disposed around thedrums, and adapted to be connected to the load, a first solenoid havinga plunger arranged between the load and first drum to move the band intodriven relationship with the first drum when the first solenoid isactuated, and a second solenoid hav- 7 ing a plunger arranged betweenthe load and second drum to move the band into driven relationship withthe second drum when the second solenoid is actuated.

3. A mechanical power amplifier capable of high speed control foramplifying power to a load comprising a rotatable power drum, anactuating band disposed around the drum, a support, a spring connectedto the support, one end of the band being connected to the spring andadapted to be connected to the load, and'a fast acting solenoid having alightweight movable plunger connected to the other end of the band tovary the strain on the band and move the band into and out of drivingrelationship with the drum when the solenoid is actuated.

References Cited in the file of this patent UNITED STATES PATENTS377,413 Smith Feb. 7, 1888 6 Nieman Mar. 25, 1930 Gretener et a1. Feb.26, 1952 Minorsky Mar. 18, 1952 Marek Jan. 20, 1953 FOREIGN PATENTSFrance Jan. 5, 1930

